As a polarizing plate used for an image display device such as a liquid crystal display device, an electro-luminescent (EL) display device, a plasma display (PD) a field emission display (FED) and the like, generally, a polarizing film including protective films bonded to both surfaces thereof is used.
Examples of the polarizing film include a polarizing film obtained by adsorbing a dichroic material such as iodine, a dichroic dye and the like to a polyvinyl alcohol-based film and further stretch-orientating the film. Examples of the protective film include a stretched product of a polycarbonate-based resin film, a stretched product of a cycloolefin-based resin film, a stretched product of a polyethylene terephthalate-based resin film, a stretched product of a polyimide-based resin film, a triacetylcellulose film or the like.
For example, a polyvinyl alcohol-based adhesive is used for laminating a transparent protective film on the polarizing film. In the lamination process, the surface of the transparent protective film to be bonded to the polarizing film is subjected to an adhesion improving treatment. The following Patent Document 1 discloses a polarizing film, in which a cycloolefin-based resin film subjected to a corona treatment is laminated on a surface of a polarizing film made of a polyvinyl alcohol-based resin with an adhesive layer interposed therebetween, and a cellulose-based resin film subjected to a saponifying treatment is laminated on the other surface of the polarizing film with an adhesive layer interposed therebetween. However, when the cycloolefin-based resin film is subjected to the corona treatment, a white fine powdery material derived from the cycloolefin-based resin is generated, which disadvantageously causes in-process contamination and defective appearance of the polarizing plate.
The following Patent Document 2 discloses a manufacturing method of subjecting a cycloolefin-based resin film to a corona treatment under an output power of 800 N or less power in order to solve such a problem. The manufacturing method can prevent the generation of the white fine powdery material derived from the cycloolefin-based resin. As a result, the manufacturing method enables manufacture of a polarizing plate suppressed in in-process contamination and defective appearance.
However, when the cycloolefin-based resin film subjected to the corona treatment is bonded to the polarizing film, sufficient tackiness is not exhibited immediately after bonding. As a result, the cycloolefin-based resin film is disadvantageously peeled from the polarizing film in the subsequent manufacturing process, or film soaring is disadvantageously generated.